1. Field of the Invention
The present invention relates generally to image forming machines and, more particularly, to a fuser for an image forming machine with a heater having a protuberance strategically placed on the surface of the heater for maintaining adequate lubricity between the belt and the heater.
2. Description of the Related Art
An image forming machine, such as a printer, copier, fax machine, all-in-one device or multifunctional device, typically includes a heating device, such as a fuser, to fix a developing agent, such as toner, to a media sheet. The fuser typically contains a heater and an endless belt and backup pressure roll that form a nip for the media sheet to pass through. They provide heat and/or pressure to the toner to soften the toner so that it will adhere to the media sheet. The fuser belt defines an inner loop. The heater is positioned within the inner loop and in direct contact with the belt. The heater has a profile generally corresponding to the travel path of the belt to provide an area contact rather than a line contact for more efficient thermal transfer. The heater is in the form of a ceramic heater held in a heater housing positioned within the inner loop and against the belt. The fuser belt is an “idling belt” having no drive rolls within it. The belt is driven by the rotation of the backup pressure roll, through the driving association of the belt with the pressure roll at the nip.
The sliding contact between the belt and the heater can cause high friction force. Lubricants such as grease and oil have commonly been used between the belt and the heater in order to reduce this high friction force.
In the prior art a problem exists in that greases normally have a higher viscosity than oil and can form a thicker film on the belt and heater surface. This higher viscosity can cause higher frictional force and driving torque. Further, the greater film thickness can cause lower fusing capability. As the grease/oil is removed from the fuser nip by the rotating action of the belt against the glass heater surface and the shear created by this action, the lubricity between the belt and the heater becomes increasingly worse. This leads to a higher driving torque, higher belt wear, and sometimes the destruction of the belt.
Thus, there is still a need for an innovation that will prevent the grease/oil form leaving the fuser nip in order to maintain the lubricity between the belt and the heater.